Optical system optimization design method for reducing inclination eccentric error sensitivity

Abstract

The invention discloses an optical system optimization design method for reducing inclination eccentricity error sensitivity, which comprises the following steps of: firstly, constructing an initial structure of an optical system according to a design index to obtain a system I; then optimizing the image quality of the system I to enable the system I to meet the nominal wavefront RMS value, and obtaining an optical system II; according to the surface shape parameter of the optical system II, a weight factor of an error sensitivity evaluation function is constructed, the error sensitivity evaluation function based on the surface shape parameter is constructed, sensitivity evaluation of the optical system II is carried out through the error sensitivity evaluation function, sensitivity reduction optimization is carried out on the optical system II according to an evaluation result, meanwhile, it is guaranteed that the system wavefront RMS is not obviously degraded, and the sensitivity of the optical system II is improved. Obtaining an optical system III; and calculating the actual wavefront RMS value of the optical system III, and determining whether to further optimize the image quality according to the actual wavefront RMS value until the design index is met, thereby completing the desensitization optimization.

Description

Technical Field

[0001] The present invention relates to the field of applied optical technologies, and particularly to an optimization design method for an optical system that reduces the sensitivity to tilt and decentration errors. Background Art

[0002] With the continuous improvement of the performance requirements of optical systems, the tolerance requirements of optical systems directly affect the realization of system design performance. The error sensitivity of an optical system characterizes the degree to which the optical system is sensitive to specific errors. Low error sensitivity can reduce the cost of optical systems, alignment difficulty, etc. Therefore, reducing the tilt and decentration error sensitivity of an optical system has an important impact on the practicality and environmental adaptability of the optical system. Currently, for the evaluation and optimization methods of the error sensitivity of optical systems, the global search method or the multiple structure optimization method of optical systems is mostly used. These two methods do not have the error sensitivity theory as a guide, have low efficiency and certain blindness, require a large amount of evaluation and optimization time, and the design cost increases. Summary of the Invention

[0003] To solve the problem that in the process of optical system design, it is difficult to comprehensively and quantitatively evaluate the error sensitivity of optical system components, resulting in strict tolerance requirements for optical component assembly and increased complexity of the alignment process, significantly increasing the alignment cost and cycle, the present invention provides an optimization design method for an optical system that reduces the tilt and decentration error sensitivity. Based on ensuring that the imaging quality index of the optical system meets the standard, by establishing an error sensitivity evaluation function, quantifying the influence of each optical surface error on the imaging performance, and synchronously suppressing the sensitivity of system errors during the optimization iteration process, the design of an optical system with low tilt and decentration error sensitivity is realized. Compared with the traditional design method that only focuses on the ideal image quality, the present invention relaxes the manufacturing tolerance and alignment accuracy requirements of optical components through active desensitization design. Under the same manufacturing process level, it not only reduces the alignment difficulty and rework rate of complex optical systems, but also improves the environmental adaptability of optical systems, thereby effectively shortening the development cycle and reducing the project cycle cost.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] An optimization design method for an optical system that reduces the tilt and decentration error sensitivity, comprising the following steps:

[0006] S1: According to the parameter requirements of the optical system index, solve the initial structure of the optical system to obtain Optical System I;

[0007] S2: Optimize the image quality of Optical System I to make the image quality of the initial structure of the optical system meet the nominal wavefront RMS value to obtain Optical System II;

[0008] S3: Construct the weight factor of the error sensitivity evaluation function according to the surface shape parameters of the optical system II:

[0009]

[0010] where, is the normalized weight factor within the surface shape region formed by the surface shape parameters, w is the optical path change within this surface shape region;

[0011] S4: Construct the error sensitivity evaluation function based on the surface shape parameters and evaluate the sensitivity of the optical system;

[0012] S5: Reduce the sensitivity of the optical system II according to the system sensitivity evaluation result in step S4 to obtain the optical system III;

[0013] S6: Calculate the actual wavefront RMS value of the optical system III. If the actual wavefront RMS value of the optical system III is greater than the nominal wavefront RMS value, return to step S2 for further image quality optimization; until the actual wavefront RMS value of the optical system III no longer decreases, the desensitization optimization of the optical system is completed.

[0014] Furthermore, in step S2, set the nominal wavefront RMS value according to the image quality optimization requirements of the optical system.

[0015] Furthermore, step S3 includes:

[0016] S31: Select the surface shape region of the optical system according to the surface shape parameters of the optical system II;

[0017] S32: According to the selected surface shape region of the optical system, construct the weight factor of the error sensitivity evaluation function; the weight factor is the optical path change of the selected surface shape region, and the calculation formula for the optical path change is:

[0018]

[0019] where, Z is the sag of the optical surface, c is the curvature, k is the conic constant, and r is the radial distance.

[0020] Furthermore, step S4 includes:

[0021] S41: Construct the error sensitivity evaluation function:

[0022]

[0023] where, S is the error sensitivity evaluation function value based on the surface shape parameters, w n is the error sensitivity weight of the nth mirror, n is the mirror serial number, N is the total number of mirrors, is the normalized curvature, is the normalized conic coefficient;

[0024] The normalization method is:

[0025]

[0026] where is the normalized curvature, is the normalized conic coefficient, |c n | is the absolute value of the curvature, k n is the conic coefficient;

[0027] S42: Evaluate the error sensitivity of the optical system II according to the error sensitivity evaluation function.

[0028] Further, in the step S42, the error sensitivity evaluation process is:

[0029] Use the error sensitivity evaluation function to evaluate the sensitivity of the optical system II, and obtain the overall error sensitivity evaluation function value of the optical system and the error sensitivity evaluation function values of each component of the optical system;

[0030] And use the evaluation function values of each component to characterize the sensitivity of each component of the optical system II, and obtain the error sensitivity distribution of each component of the optical system.

[0031] Further, in the step S5, during the desensitization optimization process of the optical system II, it is ensured that the wavefront RMS of the system does not degrade significantly, that is, the wavefront RMS value after desensitization optimization does not exceed the wavefront RMS value before optimization.

[0032] Further, the step S5 includes:

[0033] S51: Adjust the weight according to the surface shape parameters of the mirror during the desensitization optimization process, and refer to the weight factor established in the step S3 to set the weight w n ;

[0034] S52: During the iterative optimization process of desensitizing the optical system II, refer to the surface shape parameters of the optical system after the previous round of optimization before each desensitization optimization, and update the weight w n of the nth surface in the error sensitivity evaluation function, and realize the gradient guidance of the desensitization optimization path through the dynamic weight adjustment strategy.

[0035] Further, in the step S51, the radius of curvature, conic coefficient, and air gap of the initial structure of the optical system are used as optimization variables for desensitization optimization.

[0036] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0037] The present invention takes into account the influence of the components of the optical system on the sensitivity to tilt and decentration errors, and evaluates the sensitivity distribution of the optical system through the proposed error sensitivity evaluation function. The tilt and decentration error sensitivity of the optical system is optimized, realizing the design of an optical system with low tilt and decentration error sensitivity, reducing the cost and alignment difficulty of the optical system, etc. Under the same error perturbation, the environmental adaptability of the optical system is improved, and the manufacturing cost of the optical system is reduced. Description of the Drawings

[0038] Figure 1 It is a schematic flow chart of the optimization design method of the optical system for reducing tilt and decentration error sensitivity provided by an embodiment of the present invention;

[0039] Figure 2 It is a schematic diagram of the distribution of the weight factors corresponding to the surface shape interval provided by an embodiment of the present invention;

[0040] Figure 3 It is a schematic layout diagram of the optical system II after image quality optimization provided by an embodiment of the present invention;

[0041] Figure 4 It is a schematic layout diagram of the optical system III after error sensitivity optimization provided by an embodiment of the present invention;

[0042] Figure 5 It is a comparison diagram of the wavefront RMS Monte Carlo analysis of the optical system II after image quality optimization and the optical system III after error sensitivity optimization provided by an embodiment of the present invention;

[0043] Reference Signs:

[0044] 1 - Primary mirror PM of the optical system II; 2 - Secondary mirror SM of the optical system II; 3 - Tertiary mirror TM of the optical system II; 4 - Primary mirror PM of the optical system III; 5 - Secondary mirror SM of the optical system III; 6 - Tertiary mirror TM of the optical system III. Detailed Embodiment

[0045] In the following, embodiments of the present invention will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference signs. In the case of the same reference signs, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0046] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but do not constitute a limitation to the present invention.

[0047] The present invention provides an optimized design method for an optical system to reduce the sensitivity to tilt and decentration errors. First, an initial structure of the optical system is constructed according to the design specifications to obtain System I. Then, the image quality of System I is optimized to meet the nominal wavefront RMS value, obtaining Optical System II. The weight factors of the error sensitivity evaluation function are constructed based on the surface shape parameters of Optical System II, and an error sensitivity evaluation function based on the surface shape parameters is constructed. The sensitivity of Optical System II is evaluated through the error sensitivity evaluation function, and then the desensitization optimization of Optical System II is carried out according to the evaluation results, while ensuring that the wavefront RMS of the system does not degrade significantly, obtaining Optical System III. Calculate the actual wavefront RMS value of Optical System III, and determine whether to further optimize the image quality according to the actual wavefront RMS value until the design specifications are met, completing the desensitization optimization.

[0048] Figure 1 The flowchart of the optimized design method for an optical system to reduce the sensitivity to tilt and decentration errors provided by an embodiment of the present invention is shown.

[0049] As Figure 1 shown, an embodiment of the present invention provides an optimized design method for an optical system to reduce the sensitivity to tilt and decentration errors, which specifically includes the following steps:

[0050] S1: According to the optical system index parameter requirements, solve the initial structure of the optical system to obtain Optical System I; then enter step S2.

[0051] The solution of the initial structure of the optical system belongs to the prior art and can be achieved through primary aberration calculation.

[0052] S2: Optimize the image quality of Optical System I so that the image quality of the initial structure of the optical system meets the nominal wavefront RMS value, obtaining Optical System II; then enter step S3.

[0053] Set the nominal wavefront RMS value according to the image quality optimization requirements of different optical systems.

[0054] The optimization of the image quality of the initial structure of the optical system belongs to the prior art and can be achieved through optical design software.

[0055] S3: Construct the weight factors of the error sensitivity evaluation function according to the surface shape parameters of Optical System II:

[0056]

[0057] Among them, is the normalized weight factor within the surface shape region composed of the surface shape parameters, and w is the optical path change within this surface shape region.

[0058] Step S3 specifically includes the following steps:

[0059] S31: Select the optical system surface shape parameter range (surface shape region) according to the surface shape parameters of the optical system II;

[0060] S32: Construct the weight factor of the error sensitivity evaluation function according to the selected optical system surface shape parameter range; the weight factor is the optical path change of the selected surface shape parameter, and the optical path change calculation formula is:

[0061]

[0062] where Z is the sag of the optical surface, c is the curvature, k is the conic constant, and r is the radial distance.

[0063] The selected optical system surface shape parameter range and the constructed weight factor of the error sensitivity evaluation function are as Figure 2 shown.

[0064] S4: Construct an error sensitivity evaluation function based on the surface shape parameters and evaluate the sensitivity of the optical system; then enter step S5.

[0065] Step S4 specifically includes the following steps:

[0066] S41: Construct an error sensitivity evaluation function:

[0067]

[0068] where S is the error sensitivity evaluation function value based on the surface shape parameters, w n is the error sensitivity weight of the nth mirror, n is the mirror serial number, N is the total number of mirrors, is the normalized curvature, is the normalized conic constant.

[0069] The surface shape parameters in the error sensitivity evaluation function S are normalized values, and the normalization method is:

[0070]

[0071] where, is the normalized curvature, is the normalized conic constant, |c n | is the absolute value of the curvature, k n is the conic constant.

[0072] S42: Evaluate the error sensitivity of the optical system II according to the error sensitivity evaluation function.

[0073] In step S42, the specific process of error sensitivity evaluation is:

[0074] The sensitivity evaluation of the optical system II is carried out using the error sensitivity evaluation function to obtain the overall error sensitivity evaluation function value of the optical system and the error sensitivity evaluation function values of each component of the optical system; and the sensitivity of each component of the optical system II is characterized using the evaluation function values of each lens to obtain the error sensitivity distribution of each component of the optical system.

[0075] S5: The optical system II is optimized for desensitization according to the system sensitivity evaluation result of the error sensitivity evaluation function. During the desensitization optimization process, it is ensured that the wavefront RMS of the system does not degrade significantly, that is, the wavefront RMS value after desensitization optimization does not exceed the wavefront RMS value before optimization, to obtain the optical system III; then proceed to step S6.

[0076] Step S5 specifically includes the following steps:

[0077] S51: During the desensitization optimization process, the weight is adjusted according to the surface shape parameters of the mirror. As Figure 2 shown, refer to the weight factor established in step S3 to set the weight w of the nth surface in the error sensitivity evaluation function. n ;

[0078] Specifically, the radius of curvature, conic coefficient, and air gap of the initial structure of the optical system are used as optimization variables for desensitization optimization.

[0079] S52: During the iterative optimization process of desensitizing the optical system II, before each desensitization optimization, refer to the surface shape parameters of the optical system after the previous round of optimization to update the weight w of the nth surface in the error sensitivity evaluation function. n By means of a dynamic weight adjustment strategy, the gradient guidance of the desensitization optimization path is realized. Proceed to step S6.

[0080] S6: Calculate the actual wavefront RMS value of the optical system III. If the actual wavefront RMS value of the optical system III is greater than the nominal wavefront RMS value, it indicates that the image quality of the optical system III does not meet the requirements, then return to step S2 to further optimize the image quality, that is, repeat steps S2 to S5 until the actual wavefront RMS value of the optical system III no longer decreases, and the desensitization optimization of the optical system is completed.

[0081] Next, taking the optical system II as the structure to be desensitized of the optical system, the optimization effect of the optical system optimization design method for reducing the sensitivity to tilt and decentration errors is verified. As Figure 3 shown, the focal length of the off-axis three-mirror optical system is 200 mm, the F number is 6, the full field of view is 2°, and the working wavelength is 0.55 μm.

[0082] Figure 3The off-axis three-mirror optical system therein has a good nominal wavefront RMS, but a poor actual wavefront RMS. At this time, the value of the error sensitivity evaluation function of the optical system is 0.6213.

[0083] Figure 4 Fig. shows the structure of the optical system after desensitization. Finally, the value of the error sensitivity evaluation function of the optical system after desensitization is 0.4903. The selected tilt errors (meridional: 0.01°, sagittal: 0.01°) and decentration errors (meridional: 0.01 mm, sagittal: 0.01 mm) are used. Monte Carlo analysis of the wavefront RMS is used to analyze the error sensitivity of the optical system before and after desensitization. The comparison results of the Monte Carlo analysis are as Figure 5 shown. The comparison results of the evaluation function value and the wavefront RMS are shown in Table 1 below:

[0084] Table 1 Comparison results of the evaluation function value and the wavefront RMS

[0085] Non - desensitized optical system Desensitized optical system Error sensitivity function value 0.6213 0.4903 Design wavefront RMS / λ 0.0984 0.0916 Actual wavefront RMS / λ 0.1043 0.0930

[0086] According to the analysis results of the tilt and decentration error sensitivity, it can be seen that under the same error interference, the tilt and decentration error sensitivity of the optical system is reduced. For the optical system optimized by desensitization, the degradation degree of its wavefront ΔRMS is small and the standard deviation is reduced, which proves the practicability and effectiveness of the present invention.

[0087] It should be understood that the various forms of the processes shown above can be used, steps can be reordered, added or deleted. For example, the steps recorded in the disclosure of the present invention can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solutions disclosed in the present invention can be achieved. This is not limited herein.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An optical system optimization design method for reducing the sensitivity of tilt eccentricity error, characterized in that: The following steps are involved: S1: According to the optical system index parameter requirements, solve the initial structure of the optical system and obtain the optical system I; S2: Optimizing the image quality of the optical system I so that the image quality of the initial structure of the optical system meets the nominal wavefront RMS value, thereby obtaining the optical system II; S3: Construct the weight factor of the error sensitivity evaluation function according to the surface parameters of the optical system II: in, is the normalized weight factor in the surface area formed by the surface parameters, and w is the optical path change in the surface area; S4: Construct an error sensitivity evaluation function based on surface parameters and evaluate the sensitivity of the optical system; S5: Desensitize and optimize the optical system II according to the system sensitivity evaluation result of step S4 to obtain the optical system III; S6: Calculate the actual wavefront RMS value of the optical system III. If the actual wavefront RMS value of the optical system III is greater than the nominal wavefront RMS value, return to step S2 to further optimize the image quality; until the actual wavefront RMS value of the optical system III no longer decreases, the desensitization optimization of the optical system is completed.

2. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 1, characterized in that: In step S2, the nominal wavefront RMS value is set according to the image quality optimization requirement of the optical system.

3. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 1, characterized in that: The step S3 comprises: S31: selecting an optical system surface area according to the surface parameters of the optical system II; S32: According to the selected optical system surface area, a weight factor of the error sensitivity evaluation function is constructed; the weight factor is the optical path change of the selected surface area, and the optical path change calculation formula is: Among them, Z is the optical surface sagittal height, c is the curvature, k is the cone coefficient, and r is the radial distance.

4. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 1, characterized in that: The step S4 comprises: S41: Construct error sensitivity evaluation function: Where S is the error sensitivity evaluation function value based on surface parameters, w n is the error sensitivity weight of the nth reflector, n is the reflector number, N is the total number of reflectors, is the normalized curvature, is the normalized cone coefficient; The normalization method is: in, is the normalized curvature, is the normalized cone coefficient, |c n | is the absolute value of curvature, k n is the cone coefficient; S42: Evaluate the error sensitivity of the optical system II according to the error sensitivity evaluation function.

5. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 4, characterized in that: In step S42, the error sensitivity evaluation process is as follows: The error sensitivity evaluation function is used to evaluate the sensitivity of the optical system II, and the error sensitivity evaluation function value of the overall optical system and the error sensitivity evaluation function value of each component of the optical system are obtained; The sensitivity of each component of optical system II is characterized by using the evaluation function value of each component, and the error sensitivity distribution of each component of the optical system is obtained.

6. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 1, characterized in that: In step S5, during the desensitization optimization process of the optical system II, it is ensured that the system wavefront RMS has no obvious degradation, that is, the wavefront RMS value after the desensitization optimization does not exceed the wavefront RMS value before the optimization.

7. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 1, characterized in that: The step S5 comprises: S51: During the desensitization optimization process, the weight is adjusted according to the surface parameters of the reflector, and the weight w of the nth surface in the error sensitivity evaluation function is set with reference to the weight factor established in step S3. n ; S52: During the iterative optimization process of desensitizing the optical system II, before each desensitization optimization, the surface parameters of the optical system after the previous round of optimization are referred to, and the weight w of the nth surface in the error sensitivity evaluation function is updated. n ,The gradient guidance of the desensitization optimization path is achieved through a dynamic weight adjustment strategy.

8. The optical system optimization design method for reducing tilt eccentricity error sensitivity according to claim 7, characterized in that: In the step S51, the radius of curvature, cone coefficient and air gap of the initial structure of the optical system are used as optimization variables for desensitization optimization.

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